1982 Montauk 17 Weight

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MikeF1
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1982 Montauk 17 Weight

Postby MikeF1 » Sun Dec 06, 2020 11:31 am

[In order to deduce the weight of a 1982 MONTAUK 17 boat,] I weighed my tow vehicle and [empty] trailer at 5,040-lbs. Then on a different scale (but provided by the same company), I re-weighed with the 1982 Montauk 17 [on the trailer].

[From the second scale weight] the fuel weight and the weight of an additional person in my car were subtracted, and I calculated a weight of 1900-lbs for the boat [on the trailer with its] the engine (specified as 348-lbs), a battery, and a anchor. Other than those items the boat was [in the main] empty.

I'm going to live with [the MONTAUK 17] regardless [of its weight]. But [if the boat weighs 1,900-lbs as calculated above] I'm hauling a lot of water around.

Am I missing something?

BACKSTORY

The deck [of the 1982 MONTAUK 17] was compromised and soft behind the RPS when we bought the boat six years ago. An area of about 24 x 18-inches was cut out. The boat sat for about six months before the console was removed and a single piece of a 4 x 8-foot 3/8-inch thick fiberglass was custom cut and placed over the existing flat area of the deck from the transom to the fishing platform. I don't recall if the foam of the Unibond hull was cut out or if any foam was replaced. The actual work [performed in making this replair] was nicely done.

No weight measurements of the hull were measured before or after the repair.

In the water at rest, the bottom splash week drain holes well are just at the water line. I have always attributed this to the weight of the 1998 115-HP engine using a two-stroke-power-cycle design.

The MONTAUK 17 handles well and gets up on plane quickly with that 115-HP engine. I'm not sure of the top speed. The speedometer reads 42-MPH WOT with [two aboard] at an engine speed of5,200-RPM. The accuracy of these measurements is unknown to me; I don't have an accurate GNSS receiver. Fuel economy is 3 to 4 MPG.

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Phil T
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Re: 1982 Montauk 17 Weight

Postby Phil T » Sun Dec 06, 2020 1:24 pm

A key indicator of water saturation in a hull is the location of the water line at static rest.

If the water line on the transom is at the level of the splashwell drains, it is considered good. A waterline below the drains is very good. If the water line were two-inches above the drains, that would be bad.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

jimh
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Re: 1982 Montauk 17 Weight

Postby jimh » Sun Dec 06, 2020 1:32 pm

Your measurement technique is flawed by the use of different scales. Most scales that can handle weighing a vehicle that is as long as a truck with boat trailer are designed for much higher weight capacity than 5,000-lbs. A disagreement between the two scales will affect your calculated hull weight, and I would expect that an error of 100-lbs or more might have been introduced by using two different scales.

Calculating the weight of items aboard the boat can be difficult to do with accuracy. Maybe you did not add the weight of all the engine rigging, the steering wheel and helm, the remote controls, any gauges and wiring, cushions, PFD's, the anchor and mooring lines, a boat hook, and so on. There could easily be 100-lbs or more of weight you did not account for in your calculations.

A better method for determining hull weight would be to put the boat on the trailer, tow the trailer to a scale, and weigh just the trailer with boat. Then get the boat off the trailer, and return to the same scale, and weigh just the trailer.

With a more accurate hull weight, you then face the task of figuring how much the hull ought to weigh. The basis for that would be the factory specification for a 1982 MONTAUK 17. In the 1983 catalogue the specification for a 17 MONTAUK "Standard Model Boat Wt. (lbs)" is 900.

I am not clear if your calculation of boat weight at 1,900-lbs was excluding the weight of the engine, battery, and anchor. Perhaps you can clarify

Your calculated weight of 1,900-lbs suggests you have 1,000-lbs of water in the Unibond hull. One cubic-feet of water weighs 62.43-lbs, and this suggests the hull now contains 1000 / 62.43 = 16-cubic-feet of water. That volume would be roughly two-feet-wide, six-inches thick, and 16-feet long. That seems like a very large amount of water to be contained inside the Unibond hull.

biggiefl
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Re: 1982 Montauk 17 Weight

Postby biggiefl » Mon Dec 07, 2020 11:04 am

950 for dry hull, 350 for engine is 1300lbs. A trailer and some gear is easily another 600lbs. I don't see anything wrong.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

MikeF1
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Re: 1982 Montauk 17 Weight

Postby MikeF1 » Mon Dec 07, 2020 8:42 pm

I know the use of two different scales throws an unknown into the equation. I assumed, without any real basis, that [the accuracy of the two different scales] would be close. Maybe I'll go back to the original scale in the spring with my new Merc 115 4 stroke. If so, I'll report back.

These scales are used for weighing large trucks full of asphalt and other paving materials so maybe a margin of error of a few hundred pounds is acceptable. However, both times I was asked if I wanted a certified weight which would have some paperwork and a cost involved. The weighing that was done was free of cost and paperwork.

That said, I fail to see how weighing the trailer and boat without the car would make any difference. All other things being equal, the difference between the two weights is the boat.

The number I arrived at was the boat, engine, battery, anchor and very limited gear.

I'm not going to lose any sleep over [the weight I deduced]. The 1982 MONTAUK 17 isn't a pig by any means. I think If I was moving around even 600-lbs of water, the boat would be sluggish getting on plane. The previous owner aptly named it Whiplash due to the [Mercury 115-HP somewhat infamous] 2+2 engine. When the second two cylinders kick in the boat gets up and goes. I'll assume there is some water in the hull and will be satisfied with the waterline being just at the splashwell drains, as Phil said.

jimh
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Re: 1982 Montauk 17 Weight

Postby jimh » Tue Dec 08, 2020 5:40 pm

Thanks for responding to my request for clarification that the weight you deduced as 1,900-lbs was NOT for the hull, but was for the hull with the engine and other components.

jimh
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Re: 1982 Montauk 17 Weight

Postby jimh » Tue Dec 08, 2020 5:45 pm

MikeF1 wrote:...I fail to see how weighing the trailer and boat without the car would make any difference.
In your narrative, you weighed the car in both instances of getting a scale weight reading, but the total weight of the car was not the same. You probably burned off some fuel weight and you also changed the car weight by adding a passenger.

If you really want to get an accurate weight for the hull, you need to reduce variables in the weighing method to a minimum.

The method I suggested was to compare the weight just the trailer with the weight of the trailer with the boat on the trailer. The method I suggested removes the weight of the car from the calculation. Since the weight of the car was not constant, your method introduces possible errors.

My method eliminates all influence of the weight of the car on the calculation of the weight of the boat. My method also removes any ambiguity about the weight of the trailer alone since it will be measured. That weight could be useful in subsequent measurements of the weight of the boat and trailer. You only need to weigh the boat and trailer, then subtract the prior measured weight of the trailer to deduce the boat weight from a single measurement in the future.

MikeF1
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Re: 1982 Montauk 17 Weight

Postby MikeF1 » Wed Dec 09, 2020 5:44 pm

Got ya. I knew the weight of the extra person and the fuel load in the car was within a couple of gallons. My concern was in the hundreds of pounds things seemed to be off, not 10 or 20 here and there but you are right about doing it your way for the most accuracy.

ASIDE: I just got a call from the Mercury dealer and the new 115 FOURSTROKE is installed and ready to go. Unfortunately, I'll have to wait until Spring 2021 before taking out the 1982 MONTAUK 17 for a spin. Too cold to be messing about in boats now for me.